In lubricating the interface between two relatively moving surfaces a number of requirements must be met. The lubricant must be essentially chemically and physically inert with respect to the surfaces. The lubricant must reduce the force required to move one surface over the other. Lastly the lubricant must be in a form that permits the easy application of the lubricant to one or both surfaces.
Historically, lubricants were first prepared by thickening natural fats and oils with clay or chalk in order to provide sufficient lubrication for primitive wheels and axles. Upon the advent of the petroleum industry lubricant oils and greases were prepared from heavy petroleum oil fractions. In many applications petroleum lubricants are undesirable. Petroleum lubricants can interreact with many organic and inorganic substances such as plastics and rubbers, can be difficult to clean up after application, can remain in place well after application and can be unpleasant to workmen.
In view of the serious drawbacks that petroleum lubricants can have in certain applications, water based lubricants were developed. The use of many different water based lubricants is well known. More specifically, aqueous based compositions of high molecular weight polyalkylene oxide polymers have been prepared for a variety of applications including lubrication. Many other compounds have been used in preparing aqueous lubricants such as various fatty acid soaps, acrylate polymers, waxes, alkylene glycols, guar gum, Irish moss, carboxymethyl cellulose, phenolic and amineformaldehyde resins, hydrocarbon sulfonic acid, gelatin, polyurethanes, and others. See for example U.S. Pat. Nos. 3,227,652 and 3,699,057. Aqueous based lubricants are commonly more easily cleaned, more easily applied and are more agreeable to use.
To the best of my knowledge aqueous based lubricants containing many of the above mentioned compounds can suffer certain disadvantages. The lubricant compositions can be stiff, can be nonthixotropic, can be hard to handle and apply to the surfaces, the lubricant can fail to reduce the coefficient of friction under a broad load range or can be expensive.
Clearly a need exists for an inexpensive substantially inert aqueous lubricant that can be easily handled, easily applied to surfaces, having a low coefficient of friction under heavy or light load.